Given the faster and faster computer processors, technology of electronic heat dissipation has become a critical consideration in developing powerful computing. Heat transfer within a closed computer chassis utilizes thermal conduction, thermal convection and thermal radiation to guide the heat generated in a central processing unit (CPU), a graphics processing unit (GPU) or another chipset through heat sinks, heat pipes, radiator fins and fans out of the computer.
Thermo-electric coolers (TEC) are heat radiation components utilizing Peltier effect in a semiconductor, whereby heat can be delivered from a spatial point A to another spatial point B; namely, the heat at point A will be transported to point B so that the temperature at A will decrease and that at B will increase. Briefly speaking, heat is absorbed at A and released at B. A typical thermo-electric cooler is composed of a train of pairs of P type and N type semiconductor crystal granules; each of the semiconductor pairs has a metallic (copper or aluminum) conductor disposed between the P type and N type semiconductors to form a circuit loop. The bulk of semiconductor pairs is enclosed by two ceramic plates respectively on both sides of the cooler. When the cooler is charged, the N-type semiconductors will release heat, and the P-type semiconductors will absorb heat. Therefore, a cooler, made of train of N/P pairs, has a heat-absorbing terminal and a heat-releasing terminal, whereby the cooler will achieve heat dissipation by directional heat transport.
Thermo-electric coolers are often used in the heat dissipation of a central processing unit or any other heat-generating chips in a computer system. As shown in FIGS. 7 and 8, a thermo-electric cooler 5 has a heat-absorbing terminal 51 attached on a heat source 50 and a heat-releasing terminal 52 on a heat dissipation structure 90 including a heat sink and a fin set. Two interfaces of the terminals 51, 52 are applied with thermal grease for lowing the contact thermal resistance. Eventually, a fan 61 will blow wind onto the surfaces of the fins, so that forced convection within the heat dissipation structure 90 can be induced. In such an arrangement, the order of heat transportation is: heat source→thermo-electric cooler→heat sink/fins→system chassis→outer environment.
Practically, the necessary heat dissipation capacity a thermo-electric cooler needs to provide must much exceed the rated heat generating capacity of the cooler since it is electrically powered. The electric power of the cooler 5 is usually at least 30% of a central processing unit it is assigned to. According to the first law of thermodynamics, namely the conservation of energy, the rate of heat release of a cooler 5 is equal to the sum of the absorbing rate at the heat-absorbing terminal, the input electric power, and the rate of increase of internal energy. Therefore, a heat radiator equipped with a thermo-electric cooler will take away not only the heat generated by the CPU 50 (or another chipset) it is assigned to but also the electric power sent into the cooler 5. Briefly speaking, the role played by a thermo-electric cooler 5 in a heat radiator is not only a heat removing device 90 but also a significant heat source. Obviously, a heat radiator equipped with a thermo-electric cooler requires fins having a larger total surface area or a more powerful fan.